Indicator fuse for electric circuits



Oct. 25, 1966 A. J. FISTER INDICATOR FUSE FOR ELECTRIC CIRCUITS Filed Oct. 22, 1965 United States Patent O 3 281 S57 marcaron rusa iron nrnc'rnrc crncurrs Aloysius i. Fister, tlverland, Mo., assigner to McGraw- Edison Company, Elgin, Ill., a corporation of Dela- Waite Filed 9ct. 22, 1965, Ser. No. 501,123 Claims. (Cl. Zilli-121) The invention relates to improvements in protectors for electric circuits. More par-ticularly, this invention relates to improvements in electric fuses which are equipped with indicators.

Itis, therefore, an object of the present invention to provide an improved electric fuse which is equipped with an indicator.

The electric fuse provided by the present invention has an arcing compartment in which the fusible element of that fuse is disposed and has an indicating compartment in which the indicator of that fuse is normally disposed; and that electric fuse has a partition which defines and separates those two compartments. It would be desirable to equip that fuse with a partition that would make the arcing compartment tight enough to hold an arc-quenching liller but would also permit a portion of the fusible element of the fuse to pass freely through it when another portion of that fusible element fused during the blowing of that fuse. Also, it would be desirable for that partition to be made so it could be easily and inexpensively set and held in position to define the two compartments within the fuse. The present invention provides a fuse which has a partition that makes the arcing compartment of that fuse tight enough to hold arc-quenching ller, that permits a portion of the fusible element of that fuse to pass freely through it when another portion of that fusible element fuses, and that is easily and inexpensively set and held in position t-o define the arcing and indicating compartments within Ithat fuse. It is, therefore, an object of the present invention to provide an electric fuse which has a partition that makes the arcing compartment of that fuse tight enough to hold arc-quenching filler, that permits a portion of the fusible element of that fuse to pass freely through it when another portion of that fusible element fuses, and .that is easily and inexpensively set and held in position to define the arcing and indicating compartments within that fuse.

The electric fuse provided by the present invention has projections at the inner surface of the housing thereof; and those projections serve as positioning stops for the partition which separates and defines the arcing and indicating compartments of that fuse. One end of a helical compression spring urges that partition against those projections; and the other end of that spring bears against an indicator. Normally, the fusible element of the fuse is tensioned to hold the indicator in retracted position, and thus to hold the spring in a highly compressed state. However, when that fusible element fuses to open the circuit, the lspring will move the indicator into extended position to indicate that the circuit is open. A terminal cl-oses the outer end of the indicating compartment of the fuse, and that terminal has an opening in it to permit part of the indicator to project outwardly beyond that terminal when the fusible element fuses to open the circuit. The helical compression spring is made long enough to enable the said terminal to provide an initial compression of that spring which wil-l force the partition against the projections at the inner surface of the housing. That initial compression is important; because the partition includes a readily-spreadable disc which responds to the initial compression of the spring to spread into such close engagement with the inner surface of the housing that it can keep arc-extinguishing filler from leaking out of the Patented Oct. 25, 1966 ICC arcing compartment. This is very desirable; because it enables the arcing compartment to be filled with arcextinguishing tiller before the fusible element is tensioned. It is, therefore, an object 4of .the present invention to provide a fuse with a helical compression spring that coacts with an adjacent terminal to urge the partition of that fuse against projections at the inner surface of the housing of that fuse with Isufficient force to cause the spreadable disc -of that partition to spread into sealing engagement with that inner surface of that housing.

The fusible element of the electric fuse provided by the present invention is mechanically connected t0 the indicator and it is electrically bonded to one of the terminals of that fuse by solder and is electrically bonded to the other terminal of that fuse by solder and a flexible conductor. This is important because it enables that fusible element to directly control the positioning of that indicator while also providing a continuous, solder-held electrical path between the terminals of the fuse-such a path providing a desirably 10W ohmic resistance for the fuse under normal conditions. It is, therefore, an object of the present invention to provide an electric fuse with a fusible element that is mechanically connected to the indicator and is electrically bonded to one of the terminals of that fuse by solder and is electrically bonded to the other terminal of that fuse by solder and a exible conductor.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description a preferred embodiment of the present invention is shown and described but it i-s to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing, FIG. l is a side elevational view of one preferred embodiment of electric fuse that is made in accordance with the principles and teachings of the present invention,

FIG. 2 is a sectional view, on a larger scale, through the fuse of FIG. 1 and it is taken along the plane indicated by the line 2 2 in FIG. 1,

FIG. 3 is a `sectional view, 4on the scale of FIG. 2, through the upper part of the fuse of FIG. 1 before the upper terminal of that fuse is assembled with the housing of that fuse,

FIG. 4 is another sectional view, on the scale of FIG. 2, through the upper portion of the fuse of FIG. 1, and it shows that fuse after the upper terminal of that fuse has been telescoped over the upper end of the housing of that fuse, and,

FlG. 5 is an exploded view, on the scale of FIG. 2, of the fuse of FIG. l.

Referring to the drawing in detail, the numeral 20 generally denotes a preferred embodiment of electric fuse that is made in accordance with the principles and teachings of the present invention. That fuse has a housing 22 which is made of insulating material and which is cylindrical in configuration. Four protuberances or projections 2d are provided at the inner surface of the housing 22; and those protuberances are preferably formed by striking the exterior of that housing and forcing portions of the interior of the housing to deform inwardly and form those protuberances. The four protuberances 24 are in register with each other, and they serve as stops.

A stiff washer 26 of circular form has a diameter which is just slightly smaller than the inner diameter of the housing 22; and that washer is intended to abut and to be held by the protuberances 24. A disc 28 of elastomeric material -is dimensioned to tit within the housing 22; and that disc is preferably made from a thin sheet of sponge-like or foam-like elastomer. A further stiff washer 30 is dimensioned to t closely within the housing 22. As shown particularly by FIGS. 2-5, the disc 28 is intended to abut the upper face of the washer 26, and the washer 30 is intended to abut the upper face of the disc 28.

The numeral 32 denotes an elongated, small diameter, fusible element which has the upper end thereof extending through the opening in the washer 26, through an opening in the disc 28, and through the opening in the washer 38. That fusible element can be pushed through the disc 28 to form the opening in that disc. A helical compression upring 34 surrounds the upper end of the fusible element 32, and the upper end of that helical compression spring extends into a cup-like portion 38 at the bottom of an indicator 36. That indicator has an indicating portion 40 which is normally retracted, as shown by FIG. 2, but which can move into the extended position shown by FIG. 4 t-o indicate that the fusible element 32 has fused to open the circuit. An opening 42 is provided in one side of the indicating portion 40; and the upper end of the fusible element 32 passes upwardly through the cup-like portion 38, into the indicating portion 40, and then outwardly through the opening 42.

A mass 46 of solder mechanically connects the fusible element 32 to the indicator 36; and that mass of solder also electrically bonds the upper end of that fusible element to the lower end of a llexible conductor 44. That exible conductor is wound in the form of a loose helix around the indicating portion 40 of the indicator 36, and the upper end of that flexible conductor extends upwardly through an opening 50 in the end wall of a terminal 48. A mass 64 of solder will electrically bond that upper end of that flexible conductor to that terminal. The terminal 48 has an inwardly-extending recess in the end wall thereof, and it has an opening 52 at the center of that recess to accommodate the indicating portion 40 of the indicator 36.

The numeral 54 denotes another terminal for the fuse 20, and that terminal telescopes upwardly over the lower end of the housing 22. That terminal has an opening 56 therein, and it has an ear 58 that is bent outwardly from the end wall thereof. The lower end of the fusible element 32 extends through the opening in a washer 53 and through the opening 56 inthe end wall of the terminal 54 and is then bent around the ear 58 to hold it in position. Thereafter, a mass 60 of solder is used to electrically bond the lower end of that fusible element to the terminal 54.

In assembling the various components of the fuse 28, the upper end of the fusible element 32 is telescoped upwardly through the cup-like portion 38 of the indicator 36 and through the opening 42 in the indicating portion 4t). Thereafter, the upper end of the fusible element 32 is electrically bonded to the lower end of the flexible conductor 44 by the mass 46 of solder; and that mass of solder will mechanically connect that upper end to the indicator 36. The helical compression spring 34 will then be telescoped upwardly over the lower end of the fusible element 32, and the washer 38 also will be telescoped upwardly over that lower end. That lower end of that fusible element will then be forced through the spongelike or foam-like disc 28 of elastomeric material, and will then be passed through the opening in the washer 26. At this time, the flexible conductor 44, the indicator 36, the helical compression spring 34, the washer 30, the disc 2S, the washer 26, and the fusible element 32 will constitute a loosely-held sub-assembly.

The lower end of the fusible element 32 will then be threaded downwardly through the housing 22, and that fusible element will be moved far enough downwardly through that housing to cause the washer 26 to engage and be held by the protuberances or projections 24 at the interior of that housing. At this time, the helical compression spring 34 will hold all of the indicating portion 48 and part of the cup-like portion 38 outwardly of the housing 22, as shown by FIG. 3. The upper end of the flexible conductor 44 will then be threaded through the opening S0 in the end wall of the terminal 48, and the indicating portion 48 of the indicator 36 will be telescoped through the opening 52 in the recess in that end wall. The terminal 48 will then be telescoped downwardly over the upper end of the housing 22; and, as shown particularly by FIG. 4, that terminal will force the cup-like portion 38 of the indicator 36 t0 move wholly within that upper end, and it will thus initially compress the helical compression spring 34. That yinitial compression is important; because it will cause that spring t-o force the partition, which includes the elastomeric disc 28 and the washers 26 and 38, into such tight engagement with the protuberances 24 that the said elastomeric disc 'will spread into sealing engagement with the inner surface of the housing 22 and with the fusible element 32. The free end of the terminal 48 will then be crimped into locking engagement with the housing 22, as shown particularly by FIG. 2; and the upper end of the flexible conductor 44 will be bent into engagement with the end wall of that terminal and electrically bonded to it by the mass 64 of solder.

Although the indicator 36 will not 4be in its fully retracted position, the compression of the helical spring 34 will be great enough to spread the elastomeric disc 28 suiciently to force the periphery of that disc into sealing engagement with the inner surface of the housing 22 and to force the center of that disc into sealing engagement with the fusible element 32. This is important, because it enables the fuse 28 to be inverted from the position shown by FIG. 2 and to have `arc-extinguishing filler 68 introduced into the housing 22. The force of gravity will tend to urge that larc-extinguishing ller to move downwardly past the partition, which includes the washer 26, the disc 28, and the washer 30, and to enter the indicating compartment defined by the washer 30 and the end wall of the terminal 48; but the engagements between the spread-out disc 28 and the interior of the housing 22 and the surface of the fusible element 32 will be suciently intimate to prevent all such downward movement of the arc-extinguishing filler. This desirable result is obtained even though the fusible element 32 has not yet been tensioned Iand although the terminal 54 has not yet been telescoped onto the housing 22.

The space between the washer 26 and the end wall of the terminal 54 will constitute the arcing compartment of the fuse 28; and, after that arcing compartment has been filled with arc-extinguishing ller 68, the free end of the fusible element 32 will be telescoped through the opening in the washer 53 and through the opening 56 in the end wall of the terminal 54. Thereafter, that terminal `will be telescoped over the end of the housing 22 Iand will be crimped into engagement with that housing, as shown particularly by FIG. 2. The fusible element 32 will then be tensioned; and it will have a portion thereof wound around the ear 58 which is Ibent outwardly from the end wall of the terminal 54. The engagement between the bent portion of the fusible element 32 and the ear 58 will hold that fusible element in its tensioned position; and the mass 68 of solder will be applied to the Ibent portion of that fusible element and to the ear 58 to electrically bond that `fusible element to the terminal 54. As the fusible element 32 was tensioned, substantially all of the length of the indicating portion 40 of the indicator 36 was moved inwardly through the opening 52 in the end wall of the terminal 48; and, as a result, only a small part of that indicating portion will be visible.

When the circuit, which is to be protected by the fuse 28, is exposed to an undesirable overload of an undesirable duration, the fusible element 32 will fuse; and, thereupon, the helical compression spring 34 will move the indicator 36 upwardly in FIG. 2. The flexible conductor 44 will yield to permit that indicator to so move; and the center of the disc 28 also will yield to permit that indicator to so move. As that indicator moves upwardly, the indicating portion 40 thereon will move up- Wardly to the extended position shown by FIG, 4; and that portion will indicate that the fusible element 32 has fused to open the circuit. The present invention thus provides an easily-assembled, reliable, and inexpensive indicating fuse.

Whereas the drawing and Iaccompanying description have shown and described a preferred embodiment of the present invention it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

1. An electric fuse that comprises:

(a) a housing which has a plurality of projections extending inwardly from the inner surface thereof to serve as stops,

(b) said projections being integral with said housing and being deformed portions of the inner surface of said housing,

(c) a terminal that closes one end of said housing,

(d) a second terminal that closes the other end of said housing,

(e) a partition within said housing that includes a stiff washer, a disc of elastomeric material, and a second washer and that subdivides said housing into an arcing compartment and an indicating compartment,

(f) an indicator which is `disposed within said indicating compartment of said housing and that has an indicating portion which extends through an opening in the end wall of the first said terminal,

(g) a fusible element that has a portion thereof disposed within said arcing compartment of said housing, that is electrically bonded to said second terminal, and that extends through the first said washer, through said elastomeric disc, and through said second Washer of said partition,

(h) said indicator having an opening therein,

(i) said fusible element extending through said opening in said indicator,

(j) a exible conductor that is disposed within said indicating compartment of said housing, that is electrically lbonded to the first said terminal, and that is electrically bonded to said fusible element by a mass of solder,

(k) said mass of solder mechanically connecting said fusible element to said indicator,

(l) a helical compression spring that is disposed within said indicating -compartment of said housing, that surrounds part of said fusible element, that has one end thereof bearing against said indicator, and that has the other end thereof bearing against said partition,

(rn) said helical compression spring being dimensioned so it will, when the first said terminal is secured to said housing, force said partition against said projections with a force which is great enough to spread said elastomeric disc into sealing engagement with said inner surface of said housing and with said fusible element,

(n) whereby said partition can permit arc-extinguish ing filler to lbe introduced into the arcing chamber of said housing even before said fusible element is tensioned or said second terminal is secured to said housing,

(o) said flexible conductor having a generally helical configuration to permit said flexible conductor to yield readily when said fusible element fuses and thereby permit said helical compression spring to move said indicator outwardly relative to the first said terminal,

(p) said elastomeric disc being yieldable to permit said fusible element to move relative to it and thereby permit said helical compression spring to move said indicator outwardly relative to the first said terminal.

2. An electric fuse that comprises:

(a) a housing which has a plurality of projections extending inwardly from the inner surface thereof to serve as stops,

(b) said projections being integral with said housing and being deformed portions of the inner surface of said housing,

(c) a terminal that closes one end of said housing,

(d) a second terminal that closes the other end of said housing,

(e) a partition within said housing that includes a disc of elastomeric material and that subdivides said housing into an arcing compartment and an indicating compartment,

(f) an indicator which is disposed within said indicating compartment of said housing and that has an indicating portion which extends through an opening in the end wall of the first said terminal,

(g) a fusible element that has a portion thereof disposed within said arcing compartment of said housing, that is electrically bonded to said second terminal, and that extends through said elastomeric disc of said partition,

(h) a helical compression spring that is disposed within said indicating compartment of said housing, that has one end thereof bearing against said indicator, and that has the other end thereof bearing against said partition,

(i) said helical compression spring being dimensioned so it will, when the rst said terminal is secured to said housing, force said partition against said projections with a force which is great enough to spread said elastomeric disc into sealing engagement with said inner surface of said housing and with said fusible element,

(j) whereby said partition can permit arc-extinguishing filler to be introduced into the arcing chamber of said housing even before said fusible element is tensioned or said second terminal is secured to said housing,

(k) said elastomeric disc being yieldable to permit said fusible element to move relative to it and thereby permit said helical compression spring to move said indicator outwardly relative to the irst said terminal.

3. An electric fuse that comprises:

(a) a housing which has a plurality of projections extending inwardly from the inner surface thereof to serve as stops,

(b) said projections being integral with said housing and being deformed portions of the inner surface of said housing,

(c) a terminal that closes one end of said housing,

(d) a second terminal that closes the other end of said housing,

(e) a partition within said housing that subdivides said housing into an arcing compartment and an indicating compartment,

(f) an indicator which is disposed within said indicating compartment of said housing and that has an indicating portion which extends through an opening in the end wall of the first said terminal,

(g) a fusible element that has a portion thereof disposed within said arcing compartment of said housing, that is electrically bonded to said second terminal, and that extends through said partition,

(h) said partition being yieldable in part and serving, whenever it is pressed against said projections, to provide a sealing engagement with said housing and also to provide a sealing engagement with said fusible element,

(i) a helical compression spring that is disposed within said indicating compartment of said housing and that has one end thereof bearing against said partition,

(j) said helical compression spring being dimensioned so it will, when the llrst said terminal is secured to said housing, force said partition against said projections with a force which is great enough to cause said partition to provide a sealing engagement with said housing and also to provide .a sealing engagement with said fusible element,

(k) whereby said partition can permit arc-extinguishing filler to be introduced into the arcing -chamber of said housing even before said fusible element is tensioned or said second terminal is secured to said housing,

(l) said partition being yieldable to permit said fusible element to move relative to it and thereby permit said helical compression spring to move said indicator outwardly relative to the rst said terminal.

4. An electric fuse that comprises:

(a) a housing,

(b) a terminal that closes one end of said housing,

(c) a second terminal that closes the other end of said housing,

(d) a partition within said housing that subdivides said housing into an arcing compartment and an indicating compartment,

(e) lan indicator which is disposed within said indicating compartment of said housing and that has an indicating portion which extends through an opening in the end Wall of the rst said terminal,

(f) a fusible element that has a portion thereof disposed within said arcing compartment of said housing, that is electrically bonded to said second terminal, and that extends through said partition,

(g) said indicator having an opening therein,

(h) said fusible element extending through said opening in said indicator,

(i) a flexible conductor that is disposed within said indicating compartment of said housing, that is electrically bonded to the rst said terminal, and that is electrically bonded to said fusible element by a mass of solder,

(j) said mass of solder mechanically connecting said fusible element to said indicator,

(k) a helical compression spring that is disposed Within said indicating compartment of said housing,

(l) said helical compression spring being dimensioned to urge said indicator outwardly relative to the rst said terminal,

(m) said flexible conductor having a generally helical configuration to permit said flexible conductor to yield readily when said fusible element fuses and thereby permit said helical compression lspring to move said indicator outwardly relative to the first said terminal,

(n) said fusible element, said mass of solder, and said flexible conductor providing a solder-held electrical path between said terminals,

(o) whereby said electric fuse normally has a low ohmic resistance.

5. An electric fuse that comprises:

(a) a housing,

(b) a terminal at one end of said housing,

(c) a second terminal at the other end of said housing,

(d) a partition within said housing that subdivides said housing .into an arcing compartment and an indicating compartment,

(e) an indicator which is disposed within said indicating compartment of said housing and that has an indicating portion which extends through an opening in the end wall of the ilrst said terminal,

(f) a fusible element that has a portion thereof disposed within said arcing compartment of said housing, that is electrically bonded to said second terminal, and that extends through said partition,

(g) a flexible conductor that is disposed within said indicating compartment of said housing, that is electrically bonded to the rst said terminal, and that is electrically bonded to said fusible element by a mass of solder,

(h) said mass of solder mechanically connecting said fusible element to said indicator,

(i) a helical compression spring that is disposed within said indicating compartment of said housing,

(j) said helical compression spring being -dimensioned to urge said indicator outwardly relative to the rst said terminal,

(k) said flexible conductor yielding when said fusible element fuses and thereby permitting said helical compression spring to move said indicator outwardly relative to the llrst said terminal,

(l) said fusible element, said mass of sol-der, and said ilexible conductor providing a solder-held electrical path between said terminals.

References Cited by the Examiner UNITED STATES PATENTS 1,691,705 11/1928 Cook 200-121 X 1,866,491 7/1932 Schmid 200-131 2,293,953 8/ 1942 Taylor 200-120 X 2,358,676 9/1944 Wood 200-131 2,800,556 7/1957 Swain et al 200-117 X 2,834,852 5/1958 Swain et al 200-117 3,183,327 5/1965 Kozacka 20G-120 X BERNARD A. GILHEANY, Primary Examiner,

H. B. GlLSON, Assistant Examiner. 

5. AN ELECTRIC FUSE THAT COMPRISES: (A) A HOUSING, (B) A TERMINAL AT ONE END OF SAID HOUSING, (C) A SECOND TERMINAL AT THE OTHER END OF SAID HOUSING, (D) A PARTITION WITHIN SAID HOUSING THAT SUBDIVIDES SAID HOUSING INTO AN ARCING COMPARTMENT AND AN INDICATING COMPARTMENT, (E) AN INDICATOR WHICH IS DISPOSED WITHIN SAID INDICATING COMPARTMENT OF SAID HOUSING AND THAT HAS AN INDICATING PORTION WHICH EXTENDS THROUGH AN OPENING IN THE END WALL OF THE FIRST SAID TERMINAL, (F) A FUSIBLE ELEMENT THAT HAS A PORTION THEREOF DISPOSED WITHIN SAID ARCING COMPARTMENT OF SAID HOUSING, THAT IS ELECTRICALLY BONDED TO SAID SECOND TERMINAL, AND THAT EXTENDS THROUGH SAID PARTITION, (G) A FLEXIBLE CONDUCTOR THAT IS DISPOSED WITHIN SAID INDICATING COMPARTMENT OF SAID HOUSING, THAT IS ELECTRICALLY BONDED TO THE FIRST SAID TERMINAL, AND THAT IS ELECTRICALLY BONDED TO SAID FUSIBLE ELEMENT BY A MASS OF SOLDER, (H) SAID MASS OF SOLDER MECHANICALLY CONNECTING SAID FUSIBLE ELEMENT TO SAID INDICATOR, (I) A HELICAL COMPRESSION SPRING THAT IS DISPOSED WITHIN SAID INDICATING COMPARTMENT OF SAID HOUSING, (J) SAID HELICAL COMPRESSION SPRING BEING DIMENSIONED TO URGE SAID INDICATOR OUTWARDLY RELATIVE TO THE FIRST SAID TERMINAL, (K) SAID FLEXIBLE CONDUCTOR YIELDING WHEN SAID FUSIBLE ELEMENT FUSES AND THEREBY PERMITTING SAID HELICAL COMPRESSION SPRING TO MOVE SAID INDICATOR OUTWARDLY RELATIVE TO THE FIRST SAID TERMINAL, (L) SAID FUSIBLE ELEMENT, SAID MASS OF SOLDER, AND SAID FLEXIBLE CONDUCTOR PROVIDING A SOLDER-HELD ELECTRICAL PATH BETWEEN SAID TERMINALS. 